| PaperNO | Paper / Abstract |
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SE2-002
14:20
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14:40
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COMPARISON OF SEISMIC STRENGTHENING METHODS FOR SOFT-STORY RC FRAMES USING BUCKLING-RESTRAINED BRACES AND CONCRETE JACKETING
This paper focuses on comparing strengthening techniques for open ground, soft-story, RC frames using Buckling Restrained Braces (BRBs) and concrete jacketing. The effectiveness of these two strengthening methods is evaluated. Two school buildings located in northern Thailand having the same structural framing and details were strengthened using two different approaches. Background works that formed the basis for the strengthening design concepts of these buildings are briefly presented. Nonlinear analyses are used to assess the performance of the two buildings and to compare their response with that of the un-retrofitted structure. The effectiveness of using passive energy dissipating devices such as BRBs in controlling the excessive soft story drift is discussed in comparison with that of using the concrete jacketing method. The differences and limitations of the two strengthening techniques are also discussed.
Sutat Leelataviwat, Pennung Warnitchai, Hasan Tariq, Nattakan Naiyana, Wongsa Wararuksajja
Buckling Restrained Braces, concrete jacketing, School Buildings, Seismic Evaluation, Seismic Retrofitting
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SE2-023
14:40
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14:55
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SEISMIC RESPONSE OF A HALF-SCALE SEVEN-STORY REINFORCED CONCRETE STRUCTURE WITH TORSIONAL AND DAMAGE IRREGULARITIES
Past earthquakes have highlighted the vulnerability to damage of reinforced concrete buildings with torsional eccentricities/irregularities. The available evidence suggests that the primary issue in these buildings is related to large displacement demands on the flexible sides resulting in localized damage or failure of structural elements. The goal of this study is to investigate through experiments the torsional displacement demand in existing reinforced concrete buildings including the effect from nonlinear torsional response. Two series of dynamic tests were conducted on a half-scale seven-story reinforced concrete structure (with torsional irregularities at the soft first story) at the NCREE Tainan laboratory under uni-directional input from a 1999 Chi-Chi Earthquake record. The experimental program is discussed in this paper. Details of this test were also made available to researchers for a blind prediction competition to estimate displacement demands using different methods and software packages.
Tomomi Suzuki, Fu-Pei Hsiao, Aishwarya Puranam, Kenneth Elwood, Hung-Jen Lee, Ren-Jie Tsai, Shyh-Jiann Hwang
displacement demand, inelastic torsion, seismic response, Shake table test, torsional irregularity
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SE2-029
14:55
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15:10
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A PRACTICAL PROCEDURE FOR COLLAPSE RISK ASSESSMENT OF MID-TO-HIGH RISE BUILDINGS
Mid-to-high rise (MHR) buildings, which may be used as office or apartment buildings, are very common structures in urban areas. Because these buildings are usually heavily populated, the casualty and social impact caused by the collapse of these structures in an earthquake can not be overestimated. Therefore, developing a suitable assessment method to identify the buildings with high collapse risk becomes a critical issue. Even though traditional seismic assessment methods, which usually employ nonlinear static pushover analysis, have been successfully applied to regular low-rise buildings, these methods are unable to reflect higher-mode or torsional effects on the responses of an MHR building. Furthermore, a traditional approach usually leads to a deterministic result that could not account for the uncertainty in seismic motions and structural responses of an MHR building, which is usually more complicated and involves more structural uncertainties than a low-rise building. To this end, this paper presents a procedure and methodology to assess the collapse risk of an MHR building, so that high-risk buildings and their damage patterns can be identified. This methodology is developed based on the procedure of collapse fragility analysis proposed by FEMA P-58, while the collapse damage criteria and the performance indices and their acceptance criteria are adopted from relevant ASCE and FEMA document. Moreover, in establishing collapse fragility curves, this approach employs nonlinear response-history analysis together with incremental dynamic analysis (IDA) when estimating structural response parameters. Finally, for demonstration, the proposed procedure is applied to assess the collapse risk of a mid-rise RC building that collapsed in a major earthquake occurred in Taiwan, 2016.
Lyan-Ywan Lu, Fu-Pei Hsiao, Yin-Nan Huang, Wei-Huan Hsieh, Yu-Shi Tang
collapse risk, fragility analysis, incremental dynamic analysis, Mid-to-high rise building, probabilistic method, seismic assessment
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SE2-033
15:10
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15:25
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SEISMIC REPAIRING AND STRENGTHENING OF POST-TENSIONED FLAT PLATE USING POST-INSTALLED SHEAR REINFORCEMENT
This paper presents an experimental study on seismic repairing and strengthening of post-tensioned flat plate structures. A specimen of approximately 2/3 in scale was designed and built to represent an interior slab-column frame commonly used in tall buildings in Thailand. The specimen was tested under increasing cyclic lateral displacements until failure occurred and then repaired using the injection grouting method. In addition, post-installed punching shear anchors were applied from underneath the slab around the column to enhance the punching shear capacity. Finally, the specimen was re-tested using the same loading pattern. The test results before and after strengthening were compared. The specimen showed excellent behavior under cyclic loading after strengthening. Results indicated that injection grouting was a suitable and effective repairing method and that the way post-installed punching shear reinforcement was applied in this study can be used to increase the punching shear strength and, ultimately, the ductility of the slab.
Sutat Leelataviwat, Jamaluddin ChalermThai, Sumet Kietmetha
injection grouting, post-installed punching shear reinforcement, post-tensioned flat plate, seismic strengthening, slab-column frame
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SE2-004
15:25
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15:45
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STEEL FIBER REINFORCED CONCRETE COUPLING BEAMS WITH SIMPLIFIED REINFORCEMENT DETAILING: FROM RESEARCH TO PRACTICE
Reinforced Concrete coupled walls consist of two or more walls connected by short beams referred to as coupling or link beams. The coupling action provided by these beams leads to increased lateral stiffness and strength compared to isolated walls. During a seismic event, these coupling beams also represent a source of energy dissipation through inelastic deformations. In order to ensure adequate deformation capacity during earthquakes, a combination of diagonal bars and heavy confinement reinforcement is typically used in reinforced concrete coupling beams. Although it has been proven effective in terms of structural performance, this reinforcement scheme is costly and difficult to construct. As an alternative to the use of intricate diagonal and transverse reinforcement detailing in coupling beams, the use of steel fiber reinforced concrete was investigated. Several types of hooked steel fibers in volume fractions ranging between 1.0% and 1.5% were investigated. Results from reversed cyclic load tests of coupling beams with span-to-depth ratio ranging between 2.0 and 3.3 indicate that the steel fibers investigated may contribute significantly to both shear strength and deformation capacity of coupling beams, allowing the elimination of diagonal bars and substantial reductions in transverse reinforcement outside the beam plastic hinge regions. Drift capacity of coupling beams subjected to shear stress reversals of amplitude close to the upper shear stress limit in the ACI Code (0.83√f c ’ [MPa]) ranged between 5% and 7% for coupling beams with aspect ratio between 2.0 and 3.3, respectively. The elimination of diagonal reinforcement in coupling beams through the use of steel fiber reinforced concrete has attracted the attention of structural engineers and contractors during the past few years, which has led to the implementation of steel fiber reinforced concrete coupling beams in various buildings on the west coast of the USA. Ready-mix steel fiber reinforced concrete, cast in place using a crane and bucket operation, was used for the coupling beams. The construction of steel fiber reinforced concrete coupling beams in the field proved to be substantially simpler than that of coupling beams with diagonal reinforcement designed according to the ACI Building Code.
Gustavo J. Parra-Montesinos
core walls, drift, link beams, load reversals, shear, steel fibers
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